Liberals shrieked last week when President Trump proposed cutting American funding for the United Nations by 50 percent. Trump dismisses the United Nations as a “waste of time and money.” That’s the least of it.

US taxpayers bankroll the organization to the tune of $10 billion a year. Our hard-earned money perpetuates an organization that validates the most savage human rights abusers on the globe, regularly votes against America and targets America’s ally Israel for extinction.

The worst example of UN failure and waste, however, is its peacekeeping missions.

Past American presidents have poured billions into UN peacekeeping operations that have propped up autocratic regimes like those in Sudan and Angola. Worse, these so-called “peacekeepers” subject local populations to rape with stomach-turning frequency. Women and children often have more to fear from the UN’s blue-bereted soldiers than the ravages of war. Call them mission creeps.

In Haiti, UN peacekeepers dumped fecal waste into the local water supply, igniting a cholera outbreak that has killed 9,000 so far. In other strife-torn regions like Congo, peacekeepers have looked on while rival forces plunder the populace.

President Obama fancied himself a citizen of the world. Putting his naïve internationalism into practice, he elevated the United Nations above American institutions — for example, sidestepping Congress to seek UN approval of the Iran nuclear deal and the Paris climate agreement instead of seeking Senate ratification of them as treaties.

Count on Trump to reverse course and put America first. It’s even worth asking whether the United States should withdraw from the organization entirely, as veteran journalist and UN watchdog Claudia Rosett urges in her new book “What To Do About the U.N.”

Reform should start with peacekeeping. The UN Security Council has exclusive authority to approve these missions. There have been more than 50 in hotspots around the world since 1990. The United States has a Security Council veto, but too often it has failed to use it to prevent wasteful missions or redirect them to better purposes. UN forces can only go into a country if its government consents, which means peacekeepers stay for years to prop up dictatorships that have little local support. Otherwise they’re kept out altogether.

Even worse, UN forces have become notorious for raping women and children. Peacekeepers sent to the Central African Republic were accused of raping more than 100 girls in one community. Four of the girls were allegedly tied up and forced to have sex with a dog. Amnesty International for years has been drawing attention to these sexual crimes and their pervasiveness. Sexual assaults by UN personnel have been documented in Bosnia, Burundi, Cambodia, Congo, Guinea, Haiti, Kosovo, Liberia, Sierra Leone, Ivory Coast, Mali and Sudan.

Are all peacekeeping missions futile? No, but the United States should impose more ethical oversight and clearer definitions of purpose before bankrolling them.

In Lebanon, Rosett reports, UN peacekeeping forces regularly turn a blind eye as Hezbollah terrorists truck in weapons intended for use against Israel. That’s just one reason Trump’s healthy skepticism of the United Nations is welcome news for Israel. When a UN affiliate released a report last week charging Israel with operating an “apartheid state” to victimize Palestinians, US Ambassador to the UN Nikki Haley demanded its retraction — and succeeded.

The Trump administration’s unequivocal support for Israel at the United Nations is a stark improvement over Obama’s decision to sit on his hands last December, when the UN denounced Israel’s West Bank settlements. (Even worse, the Obama administration may have facilitated the anti-Israel resolution.)

Before taking office, Trump dismissed the United Nations as “just a club for people to get together, talk, and have a good time.” In fact, it’s much worse than that, and the president’s budget shows he’s ready to shake things up.

Our new president knows that self-styled global do-gooders exploit American generosity while sacrificing American interests. He’s having none of it.

Though we are the UN’s largest backer, the organization has ignored the real threats to US security. It has done nothing to halt Islamic terrorist groups like al Qaeda and ISIS, instead ginning up false claims against Israel.

Better to spend US dollars fortifying our own defense capabilities rather than on UN peacekeeping boondoggles around the globe.

Betsy McCaughey is a senior fellow at the London Center for Policy Research.